Revegetation of Weed-Infested Plant Communities
Jane Mangold
Extension Invasive Plant Specialist
Begin with the end in mind. . .
• Kill the weed—Yes, but not the whole story
• Healthy plant community that meets management objectives
Vicious (and Frustrating) Cycle
Traditional Weed Management
WEED
Biocontrol
Revegetation
Tilling/diskingMowing
Herbicides
Grazing
Fire
Hand-pulling
Fertilization
Prevention
Irrigation
Future Management
Life cycle of weed
Biocontrol
Revegetation
Tilling/disking
Mowing
Herbicides
Grazing
Fire
Hand-pulling
FertilizationPrevention
Irrigation
Plant Community
Desired Vegetation
What caused this?
What can we do to cause this?
Plant Community Undesired State
Plant Community Desired state
Necessary Components for Plant Community Change
Site Availability
Species Performance
Species Availability
Managing Plant Communities
Step 2
Determine Necessity of Revegetation
If unsure, contact local Extension, weed coordinator,
NRCS, or Conservation District office and schedule a site visit.
Is revegetation necessary?
Step 1Make a Goal Statement
Describe desired condition.
Step 3
Assess Soil and Site Properties
Are they acceptable?
Can soil be amended or are species
available that are adapted to the soil?
Step 4
Site Preparation Consider seedbed
preparation and/or soil amendments.
Are invasive weeds a
problem at the site?
Stop
Revegetation is not
recommended.
Stop
Allow natural recovery. Monitor frequently to identify
and rectify problems.Step 6
Design Seed Mix Create seed mix based on
goals and site characteristics.
Is the site a natural area?
Step 7
Determine Seeding or Planting Method
Is site accessible to equipment?
Step 8
Calculate Seeding Rate
Rates vary depending on many factors.
Always use native species when their abilities meet your
needs. Non-natives are sometimes the only choice when needs are based on considerations like forage
production and competitiveness with
invasive weeds.
Use native species to provide ecological
stability and maintain plant community
integrity.
•Hydroseed sloped sites
•Roughen soil surface before and after broadcast seeding and apply hydromulch
•Hay mulch seed
•Plant rhizome sprigs in high- salinity sites.
•Broadcast seed a non-prepared seedbed at double to triple seeding rate
•Hand-plug wetland/riparian plants.
Step 9
Determine Best Time to Seed
Indicated by selected species, method of
planting, and soil texture.
Step 10
Assist Establishment May include actions that precede or immediately follow seeding/planting.
Step 11
Monitor Monitor establishment to
identify and rectify problems in time to allow successful revegetation.
Step 12
Long-Term Management
Carefully manage to favor seeded
species.
Step 5
Reduce Weed Interference Methods vary depending on
many factors.
yes
no
yes
no
no
yes
yes
no
noyes
yes
no
Step 1—Make a goal statement
• Revegetation – Returning vegetation to a site; little emphasis on
amending ecological function• Rehabilitation
– Returning a site to a functioning state, but not necessarily its original state
– Native species not required• Restoration
– Returning a site to its original, functional state– Native species are required
difficult
very difficult
“Assisted Succession”
Restoration of weed-infested rangeland may require multiple steps
Cheatgrass/ annual forbs
Introduced, competitive grass
Native vegetation
Example Goal Statements
• Short-term goals– At the end of YR1, reduce weed cover by 25% and
increase desirable grass and forb cover by 25%.• Mid-term goals
– At the end of YR5, reduce weed cover to <20% and increase desirable grass and forb cover to >50%. Hand-pulling and or spot treatment is used to control weeds.
• Long-term goals– At the end of YR10, weeds occur only infrequently
(controlled by hand-pulling) and site is dominated by desirable grasses and forbs.
Step 2—Determine if revegetation is necessary
• Sites with >20-30% canopy cover of desired vegetation can usually recover naturally if performance of weeds is hindered
Canopy cover = area of ground covered by plant foliage
Step 3—Assess soil and site properties
• Assess soil properties to determine if they are acceptable or can be feasibly amended
Soil PropertiesSoil
parameterIdeal
conditionAcceptable
rangeMy soil
Acceptable? Yes or No
Bulk density (gm cm-3)
1.4 1.2-1.6
Soil texture (%sand, silt, clay)
Loam Clay loam to sandy loam
Salinity—EC (mm/hos/cm soluble salts)
0-2 <8
Organic matter (%)
>3 >2
pH 6.5-7.5 5.5-8.5
SAR
(Na:Ca+Mg)
<6 <12
Site Properties
• Precipitation
• Temperature
• Elevation
• Aspect
• Soil moisture – sub-irrigated– dry, upland
Step 4—Prepare site• Seedbed
– Firm enough to allow good seed-soil contact
– Loose enough to allow seed to sprout and penetrate soil
• Preparation depends on seeding method– Usually not necessary for drill seeding– Highly recommended for broadcast
seeding
•
It’s all about
balance!
Site Preparation
• Compacted soil (high bulk density)– Limits air exchange, water infiltration, and
number of safe sites– Scarify, till, disk, or plow
Site Preparation
• Chiseling or harrowing• Plowing• Disking• Dragging small chains• Limit the amount and intensity of
disturbance!– Weed like disturbance!
Do so shallowly to avoid nitrogen release
disked strips—notice brown, cured cheatgrass
Site Preparation
• Herbicide application
• Burning
• Imprinter Create safe sites
Site Preparation - Soil Amendments
• Fertilizer is typically not necessary
• Organic matter – May also decrease nitrogen availability
• Mycorrhizal innoculants
Step 5—Reduce Weed Interference
• Herbicides
• Mowing
• Grazing
• Biocontrol
• Cover crop
• Late season herbicide application combined with fall dormant seeding (single entry revegetation)
Do for a couple years prior to seeding to weaken weeds
Herbicide Selectivity
• Non-selective– Kills/stresses any plant – E.g. Roundup, Journey
• Selective– Affects some plants, but not all– Tolerance varies from species to species– E.g. 2,4-D, Tordon, Transline, Milestone, most
range and wild land herbicides
Herbicide Selectivity
• Roundup
• Tordon
• 2,4-D
• Plateau
• Transline
• Milestone
> NONE
> MODERATE
> MODERATE
> MODERATE to HIGH
> HIGH
> MODERATE
Single Entry Revegetation
Single Entry Revegetation
Control plot
• Tested on Russian knapweed in eastern OR
Single entry revegetation plot
Step 6—Design seed mix
• Avoid pre-made mixes from unknown or far away sources!
Step 6—Design seed mix
• Customize to meet goals– Forage production– Minimize erosion– Minimize weed invasion and re-establishment– Restore a healthy and diverse plant community
• Customize to site conditions– Soil properties (e.g. texture, salinity)– Precipitation, temperature, elevation, aspect, soil
moisture
Seed Mixes
• Functionally diverse– Grasses– Forbs– Shrubs
• Species-rich• Productive• Weed-free, quality seed
Increased resource capture and reduced risk of re-invasion
Step 7—Determine planting methods
• Drill– Most often preferred
• Broadcast– Steep, rocky, or remote sites
• Hydroseed– Slopes 3:1 or steeper
• Hay-mulch– Spread hay containing seeds over prepared
seedbed• “Island” seeding
Drill Seeding• Seed depth and rate are closely
controlled
• Good seed-to-soil contact
• Shortcomings
– Rows look unnatural
– Long, narrow seeds may become lodged in seeder
– Species require placement at different depths
– Seeds of different sizes separate in box—add carrier such as cracked corn or rice hulls
– Drill furrows can enhance erosion—seed along contour
Island Seeding
Distance to Recruit Patches
Reever Morghan et al. 2005. Ecological Restoration 23(3):214-215
Step 8—Calculate seeding rate
• Typically 20-50 seeds/ft2
• Determine rate based on pure live seed (PLS)• Determine rate based on seeding method and
situation– Increase rate 2-3x for broadcast seeding– Increase 2-3x for weed-infested areas
• Adjust individual species rates according to its desirable proportion of the mix
Pure Live Seed (PLS)
• Measure used by seed industry to describe the percentage of a quantity of seed that will germinate
• PLS = %purity X %viability
• Standardizes quality so puchaser can compare quality and value of different seed lots
100
Read the label!
Do the math!
• Lower $/lb., but lower purity and viability = buying more seed to achieve target seeding rate
• Higher $/lb., but higher purity and viability = buying less seed to achieve target seeding rate
Step 9—Determine best time to seed
• Cool season species– Fall-dormant during late fall
• Riparian plugs– Warm temperatures, long days, adequate
water• Late summer planting only if supplemental
water is available
Step 10—Assist establishment
• Seedling establishment is most vulnerable stage of revegetation program
• Implement management to protect sensitive seedlings– Supplemental irrigation– Defer grazing– Mulch
Step 11—Monitor progress
• Identify and fix problems in time to allow for success
• Level of monitoring increases with severity of site conditions
Step 12—Long-Term Management
• Tailor management to maintain developed plant community
• May include
– Multi-species grazing
– Allowing low-intensity disturbance, e.g. fire, proper grazing
– Controlling re-establishing weeds
Plant Community Undesired State
Plant Community Desired state
Site Availability
Species Performance
Species Availability
Information adapted from:
Revegetation Guidelines for Western Montana: Considering Invasive Weeds
by K. Goodwin, R. Sheley, and J. Marks
Montana State University Extension Bulletin 170
http://msuextension.org/publications/AgandNaturalResources/EB0170.pdf
$3/copy from Extension Publications (994-3273)
Questions? Thank you!
• For more information:
• EB0019 “Dryland Pastures in Montana and Wyoming”
http://msuextension.org/publications/AgandNatural Resources/EB0019.pdf
• Jane Mangold, Extension Invasive Plant Specialist– 994-5513; [email protected]
Plant Communities Always Change (“Succession”)
• Process whereby one plant community changes into another. It involves the immigration and extinction of species, coupled with changes in the relative abundance of different plants.-Plant Ecology by M.J. Crawley
Initial Plant Community
Site Availability
Species Performance
Species availability
Final Plant Community
Grazing
Fire
Revegetation
Biological control
Grazing
Biological control
Hand pulling
Repeated Spring Grazing
Fertilization
Mowing/cutting
Tilling
Hand pulling
Herbicide
Herbicide
Tilling improved establishment of seeded species in Russian knapweed infestation
Year 1 Year 2
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10
15
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Control Burn Till
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Mangold et al. 2007
Sheley, R. 2007. Weed Science 55:365-370
Competitive Effects of Seeded Grasses
Seeding Treatment
Perennial Grass Biomass (kg/ha)
Cheatgrass Biomass (kg/ha)
% Reduction
Critana thickspike wheatgrass
792 913 32
Bozoisky Russian wildrye
900 737 45
Sodar streambank wheatgrass
1135 207 85
Luna pubescent wheatgrass
1714 0 100
Hycrest crested wheatgrass
1596 124 91
Unseeded control --- 1337
Whitson and Koch 1998